Dead time correction of photon correlation functions

Schätzel, Klaus

doi:10.1007/bf00702660

Cited by 30 publications

(28 citation statements)

References 15 publications

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“…If the high voltage is not properly adjusted the response of the instrument is no longer linear, even for low-intensity signals, and high uncertainties are induced both in the calculation of DT and the correction of the signal. When the signal is very high (e.g., of the order of 10 7 counts s −1 ) the detection system is saturated and the measurements cannot be corrected for the nonlinear response (Kapusta et al, 2015;Schätzel, 1986). Thus, during regular operation, different neutral density (ND) attenuation filters are used to control the signal to within appropriate levels.…”

Section: The Radiation Detection Systemmentioning

confidence: 99%

“…The algorithms that have been developed for the calculation of DT and the correction of the signal are both based on Poisson statistics. According to Schätzel (1986), the average number of pulses generated within τ is given by…”

Section: The Radiation Detection Systemmentioning

confidence: 99%

“…(11) the result converges to the corrected signal N 9 I . Given the Poisson nature of photon statistics, there are two formulas that are commonly used to calculate DT (Schätzel, 1986;Yu and Fessler, 2000), which depend on the nature of the counting system. For Brewers, the relevant algorithm is based on the assumption that all photons, either recorded by the counting system or lost, trigger a new dead time period (paralyzable system) and the extended formula (Eq.…”

Section: The Radiation Detection Systemmentioning

confidence: 99%

“…8) is used. If it is assumed that the dead time is triggered only by the photons that are recorded by the counting system (nonparalyzable system) then the following, non-extended, formula applies (Schätzel, 1986;Yu and Fessler, 2000):…”

Section: The Radiation Detection Systemmentioning

confidence: 99%

“…(8) by assuming a very small value of τ and by replacing the exponential term with its Taylor expansion. Though, it describes more accurately the effect of dead time on non-paralyzable systems (Schätzel, 1986;Yu and Fessler, 2000). Subsequently, a new formula corresponding to Eq.…”

Section: The Radiation Detection Systemmentioning

confidence: 99%

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Dead time effect on the Brewer measurements: correction and estimated uncertainties

et al. 2016

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Abstract. Brewer spectrophotometers are widely used instruments which perform spectral measurements of the direct, the scattered and the global solar UV irradiance. By processing these measurements a variety of secondary products can be derived such as the total columns of ozone (TOC), sulfur dioxide and nitrogen dioxide and aerosol optical properties. Estimating and limiting the uncertainties of the final products is of critical importance. High-quality data have a lot of applications and can provide accurate estimations of trends.The dead time is specific for each instrument and improper correction of the raw data for its effect may lead to important errors in the final products. The dead time value may change with time and, with the currently used methodology, it cannot always be determined accurately. For specific cases, such as for low ozone slant columns and high intensities of the direct solar irradiance, the error in the retrieved TOC, due to a 10 ns change in the dead time from its value in use, is found to be up to 5 %. The error in the calculation of UV irradiance can be as high as 12 % near the maximum operational limit of light intensities. While in the existing documentation it is indicated that the dead time effects are important when the error in the used value is greater than 2 ns, we found that for single-monochromator Brewers a 2 ns error in the dead time may lead to errors above the limit of 1 % in the calculation of TOC; thus the tolerance limit should be lowered. A new routine for the determination of the dead time from direct solar irradiance measurements has been created and tested and a validation of the operational algorithm has been performed.Additionally, new methods for the estimation and the validation of the dead time have been developed and are analytically described. Therefore, the present study, in addition to highlighting the importance of the dead time for the processing of Brewer data sets, also provides useful information for their quality control and re-evaluation.

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Section: The Radiation Detection Systemmentioning

confidence: 99%

Section: The Radiation Detection Systemmentioning

confidence: 99%

Section: The Radiation Detection Systemmentioning

confidence: 99%

Section: The Radiation Detection Systemmentioning

confidence: 99%

Section: The Radiation Detection Systemmentioning

confidence: 99%

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Dead time effect on the Brewer measurements: correction and estimated uncertainties

et al. 2016

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High‐resolution peak analysis in TOF SIMS data

Gelb

Esfahani

Walker

2020

Surface & Interface Analysis

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High mass resolution time‐of‐flight secondary ion mass spectrometry (TOF SIMS) can provide a wealth of chemical information about a sample, but the analysis of such data is complicated by detector dead‐time effects that lead to systematic shifts in peak shapes, positions, and intensities. We introduce a new maximum‐likelihood analysis that incorporates the detector behavior in the likelihood function, such that a parametric spectrum model can be fit directly to as‐measured data. In numerical testing, this approach is shown to be the most precise and lowest‐bias option when compared with both weighted and unweighted least‐squares fitting of data corrected for dead‐time effects. Unweighted least‐squares analysis is the next best, while weighted least‐squares suffers from significant bias when the number of pulses used is small. We also provide best‐case estimates of the achievable precision in fitting TOF SIMS peak positions and intensities and investigate the biases introduced by ignoring background intensity and by fitting to just the intense part of a peak. We apply the maximum‐likelihood method to fit two experimental data sets: a positive‐ion spectrum from a multilayer MoS2 sample and a positive‐ion spectrum from a TiZrNi bulk metallic glass sample. The precision of extracted isotope masses and relative abundances obtained is close to the best‐case predictions from the numerical simulations despite the use of inexact peak shape functions and other approximations. Implications for instrument calibration, incorporation of prior information about the sample, and extension of this approach to the analysis of imaging data are also discussed.

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State of the Art and Novel Trends in Fluorescence Correlation Spectroscopy

Petrov

Schwille

Springer Series on Fluorescence

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Dead time correction of photon correlation functions

Cited by 30 publications

References 15 publications

Dead time effect on the Brewer measurements: correction and estimated uncertainties

Dead time effect on the Brewer measurements: correction and estimated uncertainties

High‐resolution peak analysis in TOF SIMS data

State of the Art and Novel Trends in Fluorescence Correlation Spectroscopy

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